1. Field of the Invention
The present invention relates to an image signal processing apparatus, a camera system and an image signal processing method, wherein an image compression technique is applied.
2. Description of the Related Art
As recent image processing apparatuses, such as a digital camera, a digital video camera and a digital television, have come to have high resolution and high definition, an amount of image data processed by an integrated circuit mounted therein has increased.
When handling enormous amounts of image data, a large amount of expensive circuit resources, such as a data bus having a wide width, a high operating frequency, and a large capacity recording device, are generally required in order to secure a band of data transfer capacity in a integrated circuit.
There also arises a hurdle of high-speed performance in the recording device as the capacity becomes larger. Particularly, in a mobile phone, a personal digital assistance (PDA), a digital camera and a portable AV player and other apparatuses required to be portable, it is required that speed performance, downsizing of an area and low power consumption are balanced, but it has become difficult to handle image data in mega-pixel units in recent years while satisfying all of the requirements at a higher order.
Therefore, generally, compression processing is performed on image data when recording it to a flash memory or other external recording device, for example, after finishing image processing in an integrated circuit.
Consequently, it becomes possible to store image data with a larger image size, or a lager amount of image data, and store image data for a longer time in an external recording device having the same capacity an compared with that in the case without compressing.
For realizing such compression processing, encoding methods, such as the JPEG, MPEG, GIF, LHA, ZIP, are used.